You should have the older kernel still on the system and should be able to choose it via the boot menu. When the new one fails to boot (get to the login screen) try the key combination CTRL/ALT F3 and see if you get a login prompt there.

You should have the older kernel still on the system and should be able to choose it via the boot menu. When the new one fails to boot (get to the login screen) try the key combination CTRL/ALT F3 and see if you get a login prompt there.

Thanks. I was able to boot using the older kernel. Bearing in mind that this was an absolutely fresh install. I ran 'yum install kernel*' and new kernel-2.6.40.6-0.fc15.x86_64 would not boot. Then I did 'yum -v install systemd systemd-sysv systemd-units' and new kernel still would not boot. Then I did 'yum -v update' which pulled over 550 packages in need of update and new kernel did boot and I was able to complete installation of nvidia driver.